The present invention relates to a semiconductor package having a case for enclosing a senor chip in a chip accommodation space, wherein the sensor chip includes, for example, a semiconductor acceleration sensor with a flexible portion supporting a plump bob.
A conventional semiconductor package for a semiconductor acceleration sensor is disclosed in, for example, Japanese Patent Publication No. 09-89925. The conventional semiconductor package comprises a resin case composed of a base plate and a sidewall provided at the periphery of the base plate. A sensor chip, or a semiconductor acceleration sensor, having a flexible portion supporting a plump bob and a signal processing chip are provided on a front surface of the base plate. The sensor chip and the signal processing chip are connected to a lead frame by wirings. A resin lid is fixed to the resin case to enclose the sensor chip and the signal processing chip in a chip accommodation space. An end portion of the lead frame is bent at an edge of the base plate of the resin case to form an outer terminal on a back surface of the base plate.
Patent Reference: Japanese Patent Publication No. 09-89925
In the conventional semiconductor package, the sensor chip and the signal processing chip are provided on the front surface of the base plate of the resin case and enclosed by the resin lid. In this configuration, a thickness of the semiconductor package is a sum of a thickness of the base plate, a height of the chip accommodation space, and a thickness of the resin lid. When the base plate of the resin case is made thin to reduce the thickness of the semiconductor package, the base plate becomes less rigid, so that the base plate may be strained under heat or upon receiving an external force. When the base plate is strained, the flexible portion supporting the plump bob of the sensor chip may be strained, thereby affecting characteristics of the sensor chip.
In the semiconductor acceleration sensor, it is necessary to provide the plump bob with a specific weight to improve accuracy of acceleration measurement. Accordingly, it is difficult to reduce the thickness of the sensor chip as opposed to other semiconductor chips. Consequently, the height of the chip accommodation space is dominantly determined by the thickness of the sensor chip, thereby making it difficult to reduce the thickness of the semiconductor package of the semiconductor acceleration sensor.
In view of the problems described above, an object of the present invention is to provide a semiconductor package with a small thickness for accommodating a sensor chip. Another object of the present invention is to provide a semiconductor package for accommodating a sensor chip, in which it is possible to reduce a strain in a base plate of the semiconductor package.
Further objects will be apparent from the following description of the invention.